Wood chip slicers commonly are of a design having an outer rotating drum with chip-cutting knives mounted therein adjoining discharge openings and having an inner anvil rotor rotating in the same direction as the drum but at a higher r.p.m. The rotor has several radial arms carrying anvils which push chips held by centrifugal force against the inside face of the drum into contact with the knives so that they are sliced, whereupon the chip slices pass outwardly through the discharge openings in the drum.
Foreign material, such as rocks and pieces of metal, are sometimes present in the wood chip material being processed and become lodged between an anvil and a knife in the slicer. The resulting jamming condition between the anvil rotor and the drum is capable of severely damaging the mechanism unless overload protection is provided. Past attempts have involved use of relatively costly pressurized units mounted on the drive shaft of the anvil rotor and designed to vent, and thereby disconnect the shaft from the anvil rotor, when subjected to a preset overload condition.